TEST 2: Verifying The Ignition Coil Activation Signal

Verifying The Ignition Coil Activation Signal. How To Test The Ignition Control Module (2.8L V6 TBI Chevrolet S10, GMC S15)

In this test section we're going to make sure that the ignition control module (ICM) is creating the ignition coil's activation signal. This activation signal is what makes the ignition coil to start sparking away.

If this test confirms that the activation signal is present, then we can conclude that the (ICM) is OK and doing its job. But if this signal is missing, then the next step is to check that the ignition control module is getting the crankshaft position signal from the pick-up coil.

NOTE: This test section requires that you crank the engine as you check for the ignition coil's activation signal. For this reason, it's important that the battery be fully charged. If the battery is low on charge, charge it up fully before you start.

OK, these are the test steps:

  1. 1

    With the 12 Volt test light, probe the white wire of the black connector. This is the wire identified the with the letter C in the image above.

    This wire connects directly to the ignition control module and the is the one that carries the ignition coil's activation signal.

    Ground the test light's crocodile type connector to your S10's battery positive (+) battery terminal.

  2. 2

    Have your helper crank the engine when you have set up the 12 Volt test light. Your job is to observe the test light.

  3. 3

    The 12 Volt test light should blink on and off when cranking the engine if the ignition control module is activating the ignition coil.

    If the ICM is not activating the ignition coil, the 12 Volt test light will not flash on and off.

Alright, let's take a look at what your test results mean:

CASE 1: The 12 Volt test light flashed on and off as your helper cranked the engine. This is means that the ignition control module is activating the ignition coil.

This test results also let you know that the pick-up coil is okay. In other words the pick-up coil is providing the crankshaft position signal to the ignition module and thus is not defective.

CASE 2: The 12 Volt test light DID NOT flash on and off as your helper cranked the engine. This test result tells you that the ignition control module is not activating the ignition coil.

The most likely cause of this missing activation signal is either a BAD ignition control module (ICM) or a BAD pick-up coil (which is the crank sensor). Your next step is to check the Pick-Up Coil's signal. For this test go to: TEST 3: Verifying The Pick-Up Coil's Signal.

TEST 3: Verifying The Pick-Up Coil's Signal

Verifying The Pick-Up Coil's Signal. How To Test The Ignition Control Module (2.8L V6 TBI Chevrolet S10, GMC S15)

As I mentioned at the beginning of this tutorial, the pickup coil is the de facto crankshaft position sensor. So, in this test section we're going to make sure that it's creating a crankshaft position signal.

If the pick-up coil's crankshaft position signal is not present, the ignition control module (ICM) will not activate the ignition coil (to start sparking away) and it also won't let the fuel injection computer know that it's time to start injecting fuel into the engine.

IMPORTANT: This test requires that you test the pickup coil signal with the engine cranking. For this reason you must take all necessary safety precautions and think safety all of the time. I strongly suggest that you use back probes to connect your multimeter to the pick-up coil's connector and be able to read your multimeter from a safe distance during the test.

OK, these are the test steps:

  1. 1

    Remove the distributor cap from the ignition distributor. The pick-up coil is located inside the distributor.

  2. 2

    Disconnect the pickup coil from the ignition control module. Using an appropriate tool, connect the red and black multimeter test leads to the pickup coils female terminals.

    NOTE: Do not insert the multimeter test leads into the pick-up coil's female terminals, or you'll damage the connectors terminals.

  3. 3

    Place your multimeter in Volts AC mode. The pickup coil creates a voltage AC signal that can be easily read with your multimeter in Volts AC mode.

  4. 4

    When the multimeter is set up, have your helper crank the engine. As the engine is turning over, observe your multimeter from a safe distance.

    As the engine is cranking, your multimeter should read a voltage between .3 to 1.8 volts AC. This voltage will fluctuate between these two values.

Alright, let's take a look at what your test results mean:

CASE 1: Your multimeter registered a voltage between .3 to 1.8 volts AC as the engine was cranking. This test result tells you that the ignition pick-up coil is creating a crankshaft position signal. So if you have confirmed all of the following:

  1. The ignition control module (ICM) is getting power in the form of 10 to 12 volts DC (TEST 1).
  2. The ignition control module is not activating the ignition coil (TEST 2).
  3. The pick-up coil is creating a crankshaft position signal (this test).

... then you can conclude that the ignition control module (ICM) is bad and needs to be replaced with a new one.

CASE 2: Your multimeter DID NOT register a voltage between .3 to 1.8 volts AC as the engine was cranking. This test result lets you know that the ignition control module is bad.

Without this crankshaft position signal, the ignition control module (ICM) will not activate the ignition coil to start sparking. The ignition module also will not inform the fuel injection computer that it's time to start injecting fuel.

Replacing the ignition pick up coil will get your pick up back on its feet. Take a look at the section: Where To Buy The Ignition Control Module And Save.